tevent: avoid any operation on epoll_ev after a epoll_panic()

tevent: avoid any operation on epoll_ev after a epoll_panic()

This calls TALLOC_FREE(ev->additional_data), which is epoll_ev
within epoll_panic() before calling the fallback handler.

In order to notice that a epoll_panic() happened, a caller can
register a pointer to a bool variable under epoll_ev->panic_state.

As epoll_check_reopen() can fail due to a epoll_panic(),
we need to force the replay flag if we have called any event handler.

Signed-off-by: Stefan Metzmacher <metze@samba.org>